Why are Warrior Axes so tiny?

[Gamemako]

I think your pictures are exaggerating. It will help get your point across much better to use actual in-game screenshots for comparison.

I took a test shot with the Bravura on my character's back. Estimating from that, it's 279 pixels from top of the blade to the lower notch (furthest visible part in the concept art) and 37 vertical pixels between corner of mouth and corner of eye. In the concept art (1920x1200), it's 323 pixels from the same locations on axe and 38 pixels from corner of eye to corner of mouth. One can surmise from this that the axe blade is actually pretty in line with concept art size. This isn't perfect, obviously, but it is a good ballpark.